The invention relates to a brush manufacturing machine with a first injection-molding machine for the region-by-region injection molding of material around bristle bundles held in cartridges and for forming a bristle carrier connecting the bristle bundle and also with a second injection-molding machine in which the bristle carrier can be inserted and material can be injection molded around this carrier for forming a brush body or partial brush body.
For the manufacturing of brushes in which the bristles are not inserted into the brush body, but in which, instead, plastic material is injection molded around the bristle bundles in the region of the brush body and these bundles are held on the brush body in this way, there is the problem that, during the injection molding of the brush body, liquid plastic material is pressed upward through the individual filaments of the bristle bundle or at the edge of the bundles due to the high injection-molding pressure and this excess plastic material is then visible at the brush surface and the brush is therefore unusable.
In order to solve this problem, different devices and methods are already known. For example, there is the option of fusing the brush bundles on their attachment side, connecting the individual fibers to each other in this way, and reinforcing the fused end.
From EP 1 110 478 A1, a method is known in which a plastic component is initially injection molded around the ends of bristle bundles projecting into a mold cavity and the bristle carrier formed in this way is then moved into a different mold cavity in which the brush body is injection molded and, in this way, material is injection molded around the bristle carrier and this carrier thus becomes a part of the brush body. Here, the bristle carrier can be injection molded with a low injection-molding pressure, so that overflowing of the injection-molding material in the region of the bristle bundle can be avoided.
The injection-molding machines are typically constructed with multi-compartment mold cavities for the simultaneous injection molding of a plurality of brush bodies, often 16 bodies for each multi-compartment mold cavity. The bristle bundles are here held in cartridges, wherein the cartridges are typically constructed as multi-compartment cartridges corresponding to the number of multi-compartment mold cavities. Such multi-compartment cartridges must be produced very precisely, especially with respect to the position of the bundle holes for the bristle bundles, and are therefore expensive, wherein the requirements on precision are greater for larger cartridges.
The injection-molding machine itself could be constructed as a multi-compartment injection-molding machine with several injection-molding assemblies, in order to be able to injection mold several plastic components one after the other, for example, a brush base body with a colored partial extrusion coating. If the first and second injection-molding machines are assembled within such a multi-compartment injection-molding machine, then three injection-molding assemblies are required for the bristle carrier, the brush base body, and the extrusion coating. Such multi-compartment injection-molding machines are very complicated and expensive, wherein the costs depend, in particular, on the number of injection-molding assemblies and, associated with this, the number of mold cavities that must be formed very precisely, wherein this number is the same for each of the partial injection-molding regions.
Because the cartridges are often still fed to processing stations after being loaded with bristle materials, for example, for profiling, grinding, and rounding of the free bristle ends and are then inserted one after the other into the individual mold cavities of the injection-molding machine, a plurality of cartridges is required. The cartridges are thus a significant cost factor for such brush manufacturing machines.